This invention relates to the production of electrically conductive polymers and is particularly concerned with the preparation of conductive polyaniline materials, particularly polyaniline materials, having high solubility in organic solvents, in combination with high conductivity.
Electrically conductive polyaniline is generally synthesized via the oxidative polymerization of aniline under aqueous acidic conditions.
Aniline is much more difficult to oxidize than the polyaniline oligomers. Consequently, the slow or rate-determining step of the reaction is the oxidation of aniline. The polyaniline product of such reaction generally contains a large percentage of polymer of very high molecular weight. However, this same product also contains some material having a relatively low molecular weight, e.g. of the order of 2,000. Unfortunately, the high molecular weight polymers are sparingly soluble in organic solvents such as N-methyl pyrrolidone (NMP), and only the low molecular weight material is soluble in organic solvents. However, the solubility of the polymers is inversely proportional to the conductivity, so that as the solubility is increased, the electrical conductivity of the polyaniline product decreases.
The solubility of high molecular weight conductive polyaniline in organic solvents has been increased by attaching specific derivatizing agents such as anhydrides to the polymer backbone. This has been described in U.S. Pat. No. 4,851,487 to S. I. Yaniger and Randy E. Cameron, and assigned to the same assignee as the present application. U.S. Pat. No. 4,855,361 to S. I. Yaniger and Randy E. Cameron, 4 and assigned to the same assignee as the present application, describes the blending of such soluble conductive polymers with polyimide resins.
The utility of conductive polymers such as conductive polyaniline is optimized when the material is highly soluble in organic solvents. This solubility allows for easy blending of the polymer with other resins such as polyimides as described in above U.S. Pat. No. 4,855,361.
U.S. patent application Ser. No. 471,979, filed Jan. 30, 1990, by R. E. Cameron and S. K. Clement, and assigned to the same assignee as the present application, discloses the preparation of controlled molecular weight conductive polyaniline having solubility in organic solvants by providing a mixture of aniline and dianiline in predetermined proportions, and reacting such mixture in the presence of a suitable oxidant such as ammonium persulfate, and a protonic acid such as tosic acid, to polymerize the mixture of aniline and dianiline. However, the resulting conductive polyaniline material still often has insufficient solubility in organic solvants such as N-methylpyrrolidone to afford optimum processibility.
An object of the present invention accordingly is the preparation of conductive polymer materials, particularly conductive polyaniline materials, having improved solubility in organic solvents and improved processibility.
Another object is the provision of conductive polymers such as conductive polyaniline having high solubility in organic solvents, in combination with high conductivity.
A still further object is the preparation of conductive polyaniline materials having the aforementioned characteristics, and also having further reactivity.
Still another object is the preparation of conductive polyaniline materials having good solubility, high conductivity and reactivity, and possessing good mechanical properties.
Yet another object is to provide novel procedure for the preparation of conductive polymers, particularly conductive polyaniline materials, having the above noted properties.